3D Printed Nozzles Turbocharge Microsphere Production

Researchers at MIT have used 3D printing to open the door to low-cost, scalable, and consistent generation of microencapsulated particles, at a fraction of the time and cost usually required. Microencapsulation is the process of encasing particles of one material (a core) within another material (a shell) and has applications in pharmaceuticals, self-healing materials, and dye-based solar cells, among others. But the main problem with the process was that it was that it was slow and didn’t scale, and it was therefore expensive and limited to high-value applications only. With some smart design and stereolithography (SLA) 3D printing, that changed. The researchers are not 3D printing these just because they can; they are printing the arrays because it’s the only way they can be made.

A standard manufacturing process for microspheres is coaxial electrospraying, where electrostatic forces and a specialized nozzle are used to encapsulate particles as they emerge from an aperture. Unfortunately, current methods have very low throughput because they have only one emitter, and must choose between low flow rate, or consistent particle size.

The researchers developed a method using a 3D printed array that is not only scalable, but consistent in output. 3D printing was needed to make the complex network of channels required for uniform operation, all at a fraction of the usual cost and fabrication time involved in testing and developing such devices.

Streams of encapsulated microspheres – each about 25 micrometers in diameter – being emitted from an array of nozzles, illuminated for the picture. Electrostatic forces drive the liquid’s movement. On the right, red is used to show the helical channel of the “shell” liquid inside the nozzle.

No mention of which SLA printer was used, but the detailed report says “The devices were fabricated using a high-resolution SLA printer (pixelation ∼25 μm) with a layer height equal to 25 μm and absolute tolerances in the x–y and z directions equal to 50 μm and 125 μm, respectively” and that the printed material is an opaque green. Do those specs sound familiar to anyone?

Someone should scale this up to something that can be printed on an FFF printer and makes “minispheres”. I’m thinking paintballs the size of Airsoft ammo. There are bound to be both culinary and pharmaceutical applications, too, just to name a few. What I’d really like is something that can withstand the heat of molten glass…

Any commercial SLA printer from the last twenty years would be capable of that resolution. The internal channels would be somewhat tricky, since the liquid resin needs to drain out, but proper design and orientation of the part in the machine can solve that problem.

I’d imagine MIT has some pretty expensive high-end machines, but FormLabs grew out of a former MIT project, and their machines are capable of this quality. There’s a chance that they used one of those, I suppose.